How does willy regard his wife?

In act one, Willy tells Linda that she is his best friend in the world and that he misses her when he is on the road. This,however, seems suspect as Willy has a mistress. Linda gives a hollow laugh to Willy's assertion that he loves her. I think that Willy's marriage has major problems. He might love his wife but the marriage seems tired and the dynamic often passive aggressive.